This will support workflows where the user can add new profiling "instruments".
Created attachment 241053 [details]
Here is a mock up on what I thought at the time I was designing the new Timelines view.
Created attachment 246234 [details]
dynamically adding timelines
I have written a patch to dynamically add/remove timelines, and will upload soon. If you want to change the UI (adding opt-in checkboxes, etc0, that can go in a different bug.
Created attachment 246237 [details]
Patch (needs rebase)
Created attachment 246239 [details]
Comment on attachment 246239 [details]
Committed r180001: <http://trac.webkit.org/changeset/180001>